Mold and method for the production of a lost-foam casting model for a light metal cylinder liner

ABSTRACT

According to the invention a light metal cylinder liner with a surface which facilitates the connection with the surrounding cast material may be produced, whereby the cylinder liner is produced by means of a lost-foam method with a form for production of the cast foam model having a structured surface with height variations of 0.8 to 5 mm, said structuring being for example grooves or longitudinal elevations.

[0001] The invention relates to a mold and a method for the production of a lost-foam casting model for a light metal cylinder liner of internal combustion engines.

[0002] It is known to cast light metal cylinder liners having an elevated silicon content in engine blocks, using the composite casting method. In this connection, it is necessary to produce a good connection, either as a positive lock or in terms of material, between the base material having a lower Si content and the cylinder liner having a higher Si content. A prerequisite for such locking together of the cylinder liner and the base material is, among other things, a rough, fissured surface of the cylinder sleeve that is to be cast into place.

[0003] In order to produce this rough and fissured surface, different methods have already been proposed: blasting, milling of depressions, or reshaping of the surface of the cylinder liner by means of pressure rollers. All of the methods require another processing step subsequent to the production of the cylinder liner by means of casting technology.

[0004] It is furthermore known from DE 3909521 to produce cylinder liners using the lost-foam method. In this connection, the lost-foam casting model is produced in a multi-part mold.

[0005] It is known from DE 19958185, which is not a prior publication, to produce a lost mold, more precisely a lost-foam casting model, having a structured outside surface, in that particles are applied adhesively to the smooth surface of a lost mold, which particles produce undercuttings when the light metal cylinder liner is cast.

[0006] The invention occupies itself with the problem of producing a light metal cylinder liner having a structured surface, in simple manner. This problem is solved in that the mold for the production of the lost-foam casting model of a cylinder liner has a structured surface with height variations of 0.8 to 5 mm, at least in partial regions. Advantageous further developments are the object of the dependent claims.

[0007] In the production of the lost-foam casting model in the mold according to the invention, a structured outside surface is formed on the model. Later, the model is embedded in casting sand and brought into connection with melt by way of a casting channel. When this is done, the model is replaced by the melt. The surface structure of the model is reproduced on the casting, forming a cylinder liner having a structured surface, without any additional machining being required.

[0008] In a standard case, the lost-foam casting model consists of polystyrene.

[0009] The height variations on the surface of the cylinder liner that form the structured surface amount to 0.8 to 5 mm, preferably 1 to 3 mm, and particularly preferably 1 to 2 mm.

[0010] In this connection, the height variations can be formed either by grooves or by elevations, and the grooves or elevations can run preferably in the axial direction, in the circumference direction, or in a diagonal direction. Furthermore, grooves and elevations can also extend in wave shape. Combinations of the stated progressions are also possible.

[0011] The grooves can be made in the mold for the production of the lost-foam casting model by means of milling, for example; the elevations can be applied by means of application welding. The erosion method is also a possibility.

[0012] The mold for the production of the lost-foam casting model must be parted in such a manner that the lost-foam casting model can be reliably unmolded. It can particularly be divided into two mold halves or four mold parts.

[0013]FIG. 1 shows a surface, according to the invention, of a mold for the production of a lost-foam casting model. The surface shows diagonally running grooves 1. Likewise, however, elevations can also be formed instead of the grooves. The surface is divided into diamond-shaped individual areas 2 by the grooves 1. 

1. Mold for the production of a lost-foam casting model for a light metal cylinder liner of internal combustion engines, characterized in that the mold has a structured surface with height variations of 0.8 to 5 mm, at least in partial regions.
 2. Mold for the production of a lost-foam casting model according to claim 1, characterized in that the structured surface is formed by grooves (1) in the surface of the mold.
 3. Mold for the production of a lost-foam casting model according to claim 1, characterized in that the structured surface is formed by elevations in the surface of the mold.
 4. Mold for the production of a lost-foam casting model according to claim 1, characterized in that the grooves (1) or elevations run in the axial direction, in the circumference direction, or in a diagonal direction, or in wave shape.
 5. Method for the production of a lost-foam casting model for a light metal cylinder liner of internal combustion engines, characterized in that the surface of the mold in which the lost-foam casting model is produced has a structured surface with height variations of 0.8 to 5 mm, at least in segments.
 6. Method according to claim 5, characterized in that the surface is structured by means of grooves (1) or elevations, which run in the axial direction, in the circumference direction, or in a diagonal direction, or in wave shape. 